Efficient warm white LED filament

Abstract

The invention provides a light generating system (1000) comprising an LED filament (100), wherein the LED filament (100) comprises an elongated carrier (410), a plurality of solid state light sources (10) configured on the elongated carrier (410), and an encapsulant (420) covering the solid state light sources (10) and at least part of the elongated carrier (410), wherein: (A) the solid state light sources (10) are configured to generate blue light source light (11); (B) the encapsulant (420) comprises (i) a first luminescent material (210) comprising one or more luminescent materials of the type A3B5O12:Ce, wherein A comprises one or more of Y, La, Gd, Tb and Lu, and wherein B comprises one or more of Al, Ga, In and Sc, (ii) a second luminescent material (220) comprising one or more luminescent materials of the type of divalent europium comprising nitride or divalent europium comprising oxynitride, and (iii) a third luminescent material (230) comprising one or more luminescent materials of the type M'xM2 -2xAX6 doped with tetravalent manganese, wherein M' comprises an alkaline earth cation, M comprises an alkaline cation, and x is selected from the range of 0-1, wherein A comprises a tetravalent cation, for instance comprising one or more of silicon and titanium, wherein X comprises a monovalent anion, at least comprising fluorine; wherein the luminescent materials (210,220,230) are configured to convert at least part of the light source light (11) into luminescent material light (211,221,231); and (C) the light generating system (1000) is configured to generate system light (1001), wherein the LED filament (100) is configured such that the system light (1001) comprises the luminescent material light (211,221,231) of the first luminescent material (210), the second luminescent material (220) and the third luminescent material (230), has a correlated color temperature of at maximum 2500 K and a color rendering index selected from the range of 65-78.

Description

[0001]2023PF80238 1 Efficient warm white LED filament FIELD OF THE INVENTION The invention relates to a light generating system. The invention further relates to a lighting device comprising the light generating system. BACKGROUND OF THE INVENTION LED filaments are known in the art. For instance, US11342311B2 describes an LED-filament comprising: a partially light-transmissive substrate; a plurality of blue LED chips mounted on a front face of the substrate; first broad-band green to red photoluminescence materials and a first narrow-band manganese-activated fluoride red photoluminescence material covering the plurality of blue LED chips and the front face of the substrate; and second broad-band green to red photoluminescence materials covering the back face of the substrate. The LED-filament can further comprise a second narrow-band manganese-activated fluoride red photoluminescence material on the back face of the substrate in an amount that is less than 5 wt % of a total red photoluminescence material content on the back face of the substrate. SUMMARY OF THE INVENTION Incandescent lamps are rapidly being replaced by light emitting diode (LED) based lighting solutions. Nevertheless, it may be appreciated and desired by users to have retrofit lamps which have the look of an incandescent bulb. A solution may be to use LED filaments. LED filaments may generally comprise a luminescent converter, wherein the luminescent converter may comprise multiple types of phosphor, such as a yellow and a red phosphor, to produce light with a suitable color temperature. Yet, known systems may suffer from low lumen per Watt efficiency, which may increase energy consumption by consumers. As such, there is a desire for lighting devices that may especially be efficient. Hence, it is an aspect of the invention to provide an alternative light generating system, which preferably further at least partly obviates one or more of above-described drawbacks. The present invention may have as object to overcome or ameliorate at least one of the disadvantages of the prior art, or to provide a useful alternative. 2023PF80238 2 According to a first aspect, the invention provides a light generating system. The light generating system may comprise a plurality of solid state light sources and a luminescent converter. In embodiments, the plurality of solid state light sources and luminescent converter may be configured as a LED filament, wherein the luminescent converter may be configured as an (elongated) encapsulant covering the plurality of solid state light sources. Yet, in (other) embodiments, the light generating system may comprise the plurality of solid state light sources and the luminescent converter, wherein the plurality of solid state light sources and the luminescent converter may not be configured as an LED filament, but e.g. like a chips on board device (including a luminescent converter). Hence, in (certain) embodiments, the light generating system may comprise an LED filament. The LED filament may especially comprise an elongated carrier, a plurality of solid state light sources configured on the elongated carrier, and an (elongated) encapsulant covering (at least some of) the solid state light sources and at least part of the elongated carrier (wherein the encapsulant may comprise the luminescent converter). In embodiments, the solid state light sources (of the light generating system, and / or of the LED filament) may be configured to generate blue light source light. Further, in embodiments, the encapsulant (and / or the luminescent converter) may comprise a first luminescent material comprising one or more luminescent materials of the type A3B5O12:Ce, wherein A comprises one or more of Y, La, Gd, Tb and Lu, and wherein B comprises one or more of Al, Ga, In and Sc. Additionally or alternatively, the encapsulant (and / or the luminescent converter) may comprise a second luminescent material comprising one or more luminescent materials of the type of divalent europium comprising nitride or divalent europium comprising oxynitride. Additionally or alternatively, the encapsulant (and / or the luminescent converter) may comprise a third luminescent material comprising one or more luminescent materials of the type M’xM2-2xAX6doped with tetravalent manganese, wherein M’ comprises an alkaline earth cation, M comprises an alkaline cation, and x may be selected from the range of 0-1, wherein A comprises a tetravalent cation, for instance comprising one or more of silicon and titanium, and wherein X comprises a monovalent anion, at least comprising fluorine. In embodiments, the (first, second, and third) luminescent materials may be configured to convert at least part of the light source light into (respectively first, second, and third) luminescent material light. Further, the light generating system may be configured to generate system light. In embodiment, the LED filament (and / or the luminescent converter) may be configured such, that the system light may comprise the luminescent material light of the first luminescent material, the second luminescent material, and the third luminescent material. Additionally, 2023PF80238 3 the system light may have a correlated color temperature (CCT) of at maximum 2500 K and a color rendering index (CRI) selected from the range of 65-78. Hence, in specific embodiments, the invention may provide a light generating system comprising an LED filament, wherein the LED filament comprises an elongated carrier, a plurality of solid state light sources configured on the elongated carrier, and an encapsulant covering the solid state light sources and at least part of the elongated carrier, wherein: (A) the solid state light sources are configured to generate blue light source light; (B) the encapsulant comprises (i) a first luminescent material comprising one or more luminescent materials of the type A3B5O12:Ce, wherein A comprises one or more of Y, La, Gd, Tb and Lu, and wherein B comprises one or more of Al, Ga, In and Sc, (ii) a second luminescent material comprising one or more luminescent materials of the type of divalent europium comprising nitride or divalent europium comprising oxynitride, and (iii) a third luminescent material comprising one or more luminescent materials of the type M’xM2-2xAX6doped with tetravalent manganese, wherein M’ comprises an alkaline earth cation, M comprises an alkaline cation, and x is selected from the range of 0-1, wherein A comprises a tetravalent cation, for instance comprising one or more of silicon and titanium, wherein X comprises a monovalent anion, at least comprising fluorine; wherein the luminescent materials are configured to convert at least part of the light source light into luminescent material light; and (C) the light generating system is configured to generate system light, wherein the LED filament is configured such that the system light comprises the luminescent material light of the first luminescent material, the second luminescent material, and the third luminescent material, has a correlated color temperature of at maximum 2500 K and a color rendering index selected from the range of 65-78. Further, in specific embodiments, the invention may provide a light generating system comprising a plurality of solid state light sources and a luminescent converter, wherein the luminescent converter is configured in a light-receiving relationship with the solid state light sources, wherein: (A) the solid state light sources are configured to generate blue light source light; (B) the luminescent converter comprises (i) a first luminescent material comprising one or more luminescent materials of the type A3B5O12:Ce, wherein A comprises one or more of Y, La, Gd, Tb and Lu, and wherein B comprises one or more of Al, Ga, In and Sc, (ii) a second luminescent material comprising one or more luminescent materials of the type of divalent europium comprising nitride or divalent europium comprising oxynitride, and (iii) a third luminescent material comprising one or more luminescent materials of the type M’xM2-2xAX6doped with tetravalent manganese, wherein 2023PF80238 4 M’ comprises an alkaline earth cation, M comprises an alkaline cation, and x is selected from the range of 0-1, wherein A comprises a tetravalent cation, for instance comprising one or more of silicon and titanium, wherein X comprises a monovalent anion, at least comprising fluorine; wherein the luminescent materials are configured to convert at least part of the light source light into luminescent material light; and (C) the light generating system is configured to generate system light, wherein the luminescent converter is configured such that the system light comprises the luminescent material light of the first luminescent material, the second luminescent material, and the third luminescent material, has a correlated color temperature of at maximum 2500 K and a color rendering index selected from the range of 65-78. With such a light generating system (comprising the LED filament and / or the luminescent converter), system light suitable for general lighting in a residential environment (e.g. a house) may be provided. Further, with such a light generating system, system light suitable for decorative applications may be provided. The composition and nature of the first luminescent material, second luminescent material, and third luminescent material in the encapsulant and / or in the luminescent converter may especially provide a light generating system having a higher lumen per Watt efficiency than known light generating systems providing system light with color rendering indices of ≥80. Hence, with such a light generating system, energy consumption may be decreased, yet a similar radiant flux may be provided (compared to known systems). In embodiments, the light generating systems may comprise one or more, such as especially a plurality of, (solid state) light sources. Hence, in embodiments, the light generating system may comprise ≥ 1, such as ≥ 5, especially ≥ 10, like ≥ 15, (solid state) light sources. Additionally or alternatively, in embodiments, the light generating system may comprise ≤ 2000, such as ≤ 1500, especially ≤ 1000, (solid state) light sources. The terms “light sources” and “solid state light sources” are further defined below, and may especially refer to one or more of light emitting diodes (LEDs), laser diodes, superluminescent diodes, and multi-junction diodes. In specific embodiments, the light sources may be LEDs. The light source(s) may be configured to generate light source light. In embodiments, the light source light may have a (first) peak wavelength λp1. The (first) peak wavelength λp1may in embodiments be selected from the range of 380-490 nm, such as from the range of 400-480 nm, especially from the range of 420-470 nm, like from the range of 440-465 nm. Hence, in embodiments, the (solid state) light sources may be configured to generate violet and / or blue light source light, such as especially blue light source light. Additionally or alternatively, the 2023PF80238 5 light source light may have a spectral power distribution with intensity in one or more of the violet and blue wavelength range. The term “violet light”, and similar terms, may especially relate to light having a wavelength in the range of about 380-440 nm. The term “blue light”, and similar terms, may especially relate to light having a wavelength in the range of about 440-490 nm. In embodiments, the (blue) light source light may be incident on a luminescent converter. Hence, in embodiments, the light generating system may comprise a luminescent converter configured downstream of the (solid state) light source(s). The terms “downstream” and “upstream” relate to an arrangement of items or features relative to the propagation of the light from a light generating means (here the especially the light source), wherein relative to a first position within a beam of light from the light generating means, a second position in the beam of light closer to the light generating means is “upstream”, and a third position within the beam of light further away from the light generating means is “downstream”. In embodiments, the luminescent converter may be configured on top of the light sources, such as especially in physical contact with the light sources. Especially, in embodiments the light generating system may comprise a LED filament, wherein the luminescent converter may be configured as an encapsulant covering the (solid state) light source (see below). Alternatively, the luminescent converter may be configured at a non-zero distance d1from the light source(s). Especially, the light sources may have a face, such as a face comprising a light escape surface (see below). In embodiments, the luminescent converter may be configured at a distance d1from said face of the light sources. In embodiments, the distance d1may be selected from the range of ≥ 5 µm, such as from the range of ≥ 15 µm, especially from the range of ≥ 50 µm. Further, the distance d1may be selected from the range of ≤ 50 cm, such as from the range of ≤ 30 cm, especially from the range of ≤ 10 cm. Further, in specific embodiments, the luminescent converter may be physically separated from the light sources. In embodiments, the luminescent converter may comprise the first luminescent material, the second luminescent material, and the third luminescent material. The term “luminescent material” may especially refer to a material that can convert first radiation, especially one or more of UV radiation and blue radiation, into second radiation. In general, the first radiation and second radiation have different spectral power distributions, with the second radiation generally having a spectral power distribution at larger wavelengths than the first radiation (i.e. “down-conversion”). The terms “light” and “radiation” are herein interchangeably used, unless clear from the context that the term “light” only refers to visible light. The terms “light” and “radiation” may thus refer to UV 2023PF80238 6 radiation, visible light, and IR radiation. In specific embodiments, especially for lighting applications, the terms “light” and “radiation” refer to (at least) visible light. In embodiments, the “luminescent material” may especially refer to a material that can convert radiation into e.g. visible and / or infrared light. For instance, in embodiments the luminescent material may be able to convert one or more of UV radiation and blue radiation, into visible light. The terms “visible”, “visible light” or “visible emission” and similar terms refer to light having one or more wavelengths in the range of about 380-780 nm. Herein, UV (ultraviolet) may especially refer to a wavelength selected from the range of 190-380 nm, such as 200-380 nm, though in specific embodiments other wavelengths may also be possible. Hence, upon excitation with radiation, the luminescent material may emit radiation. In embodiments, the term “luminescence” may refer to phosphorescence. In embodiments, the term “luminescence” may also refer to fluorescence. Instead of the term “luminescence”, also the term “luminescent material light” or “emission” may be applied. Hence, the terms “first radiation” and “second radiation” may refer to excitation radiation and emission (radiation), respectively. Likewise, the term “luminescent material” may in embodiments refer to phosphorescence and / or fluorescence. The term “luminescent material” may also refer to a plurality of different luminescent materials. Examples of possible luminescent materials are indicated below. Hence, the term “luminescent material” may in specific embodiments also refer to a luminescent material composition. Instead of the term “luminescent material” also the term “phosphor” may be applied. These terms are known to the person skilled in the art. In embodiments, luminescent materials may be selected from garnets and nitrides, especially doped with trivalent cerium or divalent europium, respectively. The term “nitride” may also refer to oxynitride or nitridosilicate, etc. Alternatively or additionally, the luminescent material(s) may be selected from silicates, especially doped with divalent europium. In embodiments, the luminescent material may comprise a divalent europium comprising oxynitride luminescent material. Further, in embodiments, the luminescent material may comprise a divalent europium comprising nitride luminescent material. In specific embodiments, the luminescent material may at least comprise a luminescent material of the type A3B5O12:Ce, wherein A comprises one or more of Y, La, Gd, Tb and Lu, and wherein B comprises one or more of Al, Ga, In and Sc; and wherein the light source light may comprise blue light source light. Especially, A may comprise one or more of Y, Gd and Lu, such as especially one or more of Y and Lu. Especially, B may comprise one or more of Al and Ga, more especially at least Al, such as essentially entirely Al. Hence, especially suitable luminescent materials are cerium comprising garnet materials. 2023PF80238 7 Embodiments of garnets especially include A3B5O12garnets, wherein A comprises at least yttrium (Y) or lutetium (Lu) and wherein B comprises at least aluminum (Al). Such garnets may be doped with cerium (Ce), with praseodymium (Pr) or a combination of cerium and praseodymium; especially however with Ce. In another variant, B and O may at least partly be replaced by Si and N. The element A may especially be selected from the group consisting of yttrium (Y), gadolinium (Gd), terbium (Tb) and lutetium (Lu). Further, Gd and / or Tb are especially only present up to an amount of about 20% of A. In a specific embodiment, the garnet luminescent material comprises (Y1-xLux)3B5O12:Ce, wherein x is equal to or larger than 0 and equal to or smaller than 1. The term “:Ce”, indicates that part of the metal ions (i.e. in the garnets: part of the “A” ions) in the luminescent material is replaced by Ce. For instance, in the case of (Y1-xLux)3Al5O12:Ce, part of Y and / or Lu is replaced by Ce. This is known to the person skilled in the art. Ce will replace A in general for not more than 10%; in general, the Ce concentration will be in the range of 0.1 to 4%, especially 0.1 to 2% (relative to A). Assuming 1% Ce and 10% Y, the full correct formula could be (Y0.1Lu0.89Ce0.01)3Al5O12. Ce in garnets is substantially or only in the trivalent state, as is known to the person skilled in the art. In embodiments, the luminescent material (thus) comprises A3B5O12wherein in specific embodiments at maximum 10% of B-O may be replaced by Si-N. Such luminescent materials may have a suitable spectral distribution, have a relatively high efficiency, have a relatively high thermal stability, and allow a high CRI (optionally in combination with (the) light of other sources of light as described herein). In specific embodiments, the luminescent material may only include luminescent materials selected from the type of cerium comprising garnets. In even further specific embodiments, the luminescent material may include a single type of luminescent material, such as (Yx1A’x2Cex3)3(Aly1B’y2)5O12. Hence, in specific embodiments the first luminescent material may comprise luminescent material, wherein at least 85 weight%, even more especially at least about 90 wt.%, such as yet even more especially at least about 95 weight % of the luminescent material comprises (Yx1A’x2Cex3)3(Aly1B’y2)5O12. Here, A’ comprises one or more elements selected from the group consisting of lanthanides, and B’ comprises one or more elements selected from the group consisting of Ga, In and Sc, wherein x1+x2+x3=1, wherein x3>0, wherein 0<x2+x3≤0.2, wherein y1+y2=1, wherein 0≤y2≤0.2. Especially, x3 is selected from the range of 0.001-0.1. Note that in embodiments x2=0. Alternatively or additionally, in embodiments y2=0. In embodiments, the luminescent material may comprise a luminescent material of the type A3Si6N11:Ce3+, wherein A comprises one or more of Y, La, Gd, Tb and 2023PF80238 8 Lu, such as in embodiments one or more of La and Y. In embodiments, the luminescent material may alternatively or additionally comprise one or more of MS:Eu2+and / or M2Si5N8:Eu2+and / or MAlSiN3:Eu2+and / or Ca2AlSi3O2N5:Eu2+, etc., wherein M comprises one or more of Ba, Sr and Ca, especially in embodiments at least Sr. Hence, in embodiments, the luminescent material may comprise one or more materials selected from the group consisting of (Ba,Sr,Ca)S:Eu, (Ba,Sr,Ca)AlSiN3:Eu and (Ba,Sr,Ca)2Si5N8:Eu. In these compounds, europium (Eu) is substantially or only divalent, and replaces one or more of the indicated divalent cations, as is known to the person skilled in the art. In general, Eu will not be present in amounts larger than 10% of the cation; its presence will especially be in the range of about 0.5 to 10%, more especially in the range of about 0.5 to 5% relative to the cation(s) it replaces. The term “:Eu”, indicates that part of the metal ions (indicated by M) is replaced by Eu (in these examples by Eu2+). For instance, assuming 2% Eu in CaAlSiN3:Eu, the correct formula could be (Ca0.98Eu0.02)AlSiN3. The term “luminescent material” herein especially relate to inorganic luminescent materials. Alternatively or additionally, also other luminescent materials may be applied. For instance quantum dots and / or organic dyes may be applied and may optionally be embedded in transmissive matrices like e.g. polymers, like PMMA, or polysiloxanes, etc. In embodiments, the luminescent material may comprise a luminescent material of the type M’xM2-2xAX6doped with tetravalent manganese, wherein M’ comprises an alkaline earth cation, M comprises an alkaline cation, and x may be selected from the range of 0-1, wherein A comprises a tetravalent cation, for instance comprising one or more of silicon and titanium, wherein X comprises a monovalent anion, at least comprising fluorine. Such luminescent materials may herein also be indicated as “KSiF” or “KSF”, whether or not M comprises K or one or more other alkaline cations. A luminescent material of the type M’xM2-2xAX6doped with tetravalent manganese is amongst others described in WO2013121355A1, which is herein incorporated by reference. Passages from WO2013121355A1 are also copied herein. Relevant alkaline earth cations (M’) are magnesium (Mg), strontium (Sr), calcium (Ca) and barium (Ba), especially one or more of Sr and Ba. Relevant alkaline cations (M) are sodium (Na), potassium (K) and rubidium (Rb). Optionally, also ammonium (NH4+), lithium (Li) and / or cesium (Cs) may be applied. In a preferred embodiment, M comprises at least potassium. In yet another embodiment, M comprises at least rubidium. In another preferred embodiment, M comprises at least potassium and rubidium. Optionally, the M’xM2-2xAX6luminescent material has the hexagonal phase. In yet another embodiment, the M’xM2-2xAX6luminescent material has the 2023PF80238 9 cubic phase. In an embodiment, a combination of different alkaline cations may be applied. In yet another embodiment, a combination of different alkaline earth cations may be applied. In yet another embodiment, a combination of one or more alkaline cations and one or more alkaline earth cations may be applied. For instance, KRb0.5Sr0.25AX6might be applied, wherein x may be selected from the range of 0-1, especially x ≤ 1. In specific embodiments, x = 0. The term “tetravalent manganese” refers to Mn4+. This is a well-known luminescent ion. In the formula as indicated above, part of the tetravalent cation A (such as Si) is being replaced by manganese. Hence, M’xM2-2xAX6doped with tetravalent manganese may also be indicated as M’xM2-2xA1-mMnmX6. The mole percentage of manganese, i.e. the percentage it replaces the tetravalent cation A will in general be in the range of 0.1-15 %, especially 1-12 %, i.e. m is in the range of 0.001-0.15, especially in the range of 0.01-0.12. As manganese replaces part of a host lattice ion and has a specific function, it is also indicated as “dopant” or “activator”. Hence, the hexafluorosilicate is doped or activated with manganese (Mn4+). In embodiments, A may comprise a tetravalent cation, and preferably at least comprises silicon. A may optionally (further) comprise one or more of titanium (Ti), germanium (Ge), stannum (Sn) and zinc (Zn). Preferably, at least 80%, even more preferably at least 90%, such as at least 95% of A consists of silicon. As indicated above, X relates to a monovalent anion, but at least comprises fluorine. Other monovalent anions that may optionally be present may be selected from the group consisting of chlorine (Cl), bromine (Br), and iodine (I). Preferably, at least 80%, even more preferably at least 90%, such as 95% of X consists of fluorine. Especially, X essentially consists of F (fluorine). In an embodiment, M’xM2-2xAX6comprises K2SiF6(indicated herein also as KSiF system). In another preferred embodiment, M’xM2-2xAX6comprises KRbSiF6(herein also indicated as K,Rb system). In specific embodiments, the indication M’xM2-2xAX6may refer to one or more of (K,Rb)2SiF6:Mn4+, (K,Rb)2TiF6:Mn4+, K2(Si,Ti)F6:Mn4+, and Rb2(Si,Ti)F6:Mn4+, such as one or more of K2TiF6:Mn4+, of K2SiF6:Mn4+, and of Rb2SiF6:Mn4+. As can be derived from the above, “(Si,Ti)” may indicate one or more of Si and Ti. Hence, in specific embodiments, the luminescent material may comprise one or more of (K,Rb)2SiF6:Mn4+and K2(Si,Ti)F6:Mn4+. The luminescent material may also be coated, as also described in WO2013121355A1. In embodiments, the first luminescent material may comprise (or be) a luminescent material selected from the group of (cerium comprising) garnets. Especially, in embodiments, the first luminescent material may comprise one or more luminescent materials of the type A3B5O12:Ce, wherein A comprises one or more of Y, La, Gd, Tb and Lu, and wherein B comprises one or more of Al, Ga, In and Sc. In (such) embodiments, A may at 2023PF80238 10 least comprise Lu. Hence, in specific embodiments, the first luminescent material may comprise a luminescent material of the type A3B5O12:Ce, wherein A at least comprises Lu. Such a luminescent material may have a relatively high efficiency and / or a relatively high thermal stability. Further, such a luminescent material may provide luminescent material light having intensity in the green and / or yellow wavelength range (see below). In embodiments wherein the first luminescent material comprises a luminescent material of the type A3B5O12:Ce wherein A at least comprises Lu, B may in embodiments be (essentially) free of Ga. That is, in embodiments, the first luminescent material may comprise a luminescent material of the type A3B5O12:Ce, wherein said luminescent material may comprise one of Lu and Ga, and may not comprise the other of Lu and Ga. Yet, in embodiments, the first luminescent material may comprise a luminescent material of the type A3B5O12:Ce, wherein A at least comprises Lu, and wherein B at least comprises Ga. Additionally or alternatively, in embodiments, the first luminescent material may comprise one or more luminescent materials of the type A3B5O12:Ce, wherein A at least comprises Y, and wherein B comprises one or more of Al, Ga, In and Sc. Further, in embodiments, the first luminescent material may (at least) comprise a luminescent material of the type A3B5O12:Ce, wherein A at least comprises one or more of Y and Gd, and wherein B at least comprises Ga. Further, in specific embodiments, the first luminescent material may especially comprise a luminescent material of the type A3B5O12:Ce, wherein at least a third of B may consist of Ga, such as in embodiments at least 90%, or even 100%. In specific embodiments, the first luminescent material may especially comprise a luminescent material of the type A3B5O12:Ce, wherein at least a third of A may consist of Y, and wherein at least a third of B may consist of Ga. Hence, in specific embodiments, the first luminescent material may comprise a luminescent material of the type A3B5O12:Ce, wherein A at least comprises Y, and wherein B at least comprises Ga. Such a luminescent material may have a relatively high efficiency and / or a relatively high thermal stability. Percentages or the indication of “a third" refer to atomic ratios. For instance, the indication “A3B5O12:Ce, wherein at least a third of A may consist of Y, and wherein at least a 90% of B may consist of Ga”, may e.g. refer to (Y0.33Gd0.66)3(Al0.1Ga0.9)5O12:Ce or e.g. Y3Ga5O12:Ce, etc. In embodiments, the first luminescent material may be configured to convert at least part of the (blue) light source light received by the first luminescent material into first luminescent material light. Especially, the (blue) light source light may have a spectral power distribution, wherein the light generating system (especially the LED filament) may be configured such that at least 7%, such as at least 10%, especially at least 15%, like at least 2023PF80238 11 18%, of the spectral power of the (blue) light source light may be converted by the first luminescent material. Additionally or alternatively, the light generating system may be configured such that at most 95%, such as at most 90%, especially at most 85%, like at most 80%, of the spectral power of the (blue) light source light may be converted by the first luminescent material. In embodiments, the first luminescent material light generated by the first luminescent material may have a first centroid wavelength λc1. The term “centroid wavelength”, also indicated as λc, is known in the art, and refers to the wavelength value where half of the light energy is at shorter and half the energy is at longer wavelengths; the value is stated in nanometers (nm). It is the wavelength that divides the integral of a spectral power distribution into two equal parts as expressed by the formula λc = Σ λ*I(λ) / (Σ I( λ)), where the summation is over the wavelength range of interest, and I(λ) is the spectral energy density (i.e. the integration of the product of the wavelength and the intensity over the emission band normalized to the integrated intensity). The centroid wavelength may e.g. be determined at operation conditions. In embodiments, the first centroid wavelength λc1(of the first luminescent material) may be selected from the range of 490-590 nm, such as from the range of 500-590 nm, especially from the range of 510-590 nm, like from the range of 530- 590 nm (like from the range of 530-585 nm). Hence, in embodiments, the first luminescent material may be configured to generate one or more of green and yellow first luminescent material light. That is, the first luminescent material light may be one or more of green light and yellow light. The terms “green light” or “green emission”, and similar terms, may especially relate to light having a wavelength in the range of about 490-560 nm. The terms “yellow light” or “yellow emission”, and similar terms, may especially relate to light having a wavelength in the range of about 560-590 nm. In embodiments, the second luminescent material may comprise one or more luminescent materials of the type of divalent europium comprising nitride or divalent europium comprising oxynitride. Additionally or alternatively, in embodiments, the second luminescent material may comprise one or more luminescent materials of the type of (red (light emitting)) silicate phosphors and (red (light emitting)) sulfide phosphors. Examples of suitable luminescent materials may be (Ba,Sr,Ca)AlSiN3:Eu, (Ba,Sr,Ca)2Si5N8:Eu, and SrLi2Si2Al2O2N2:Eu. Hence, in specific embodiments, the second luminescent material may comprise one or more of (Ba,Sr,Ca)AlSiN3:Eu, (Ba,Sr,Ca)2Si5N8:Eu, and SrLi2Si2Al2O2N2:Eu. Such luminescent materials may provide luminescent material light having a broad spectral power distribution with intensity in the yellow, orange, and red wavelength range. Further, such luminescent materials may be relatively efficient. 2023PF80238 12 In embodiments, the second luminescent material may be configured to convert at least part of the (blue) light source light received by the second luminescent material into second luminescent material light. Especially, the (blue) light source light may have a spectral power distribution, wherein the light generating system (especially the LED filament) may be configured such that at least 3%, such as at least 5%, especially at least 10%, of the spectral power of the (blue) light source light may be converted (into second luminescent material light) by the second luminescent material. Additionally or alternatively, the light generating system may be configured such that at most 50%, such as at most 40%, especially at most 30%, of the spectral power of the (blue) light source light may be converted (into second luminescent material light) by the second luminescent material. Additionally or alternatively, the second luminescent material may be configured to convert at least part of the (yellow-green) first luminescent material light received by the second luminescent material into second luminescent material light. Especially, the first luminescent material light may have a spectral power distribution over a first wavelength range, wherein the second luminescent material may be configured to convert at least part of the spectral power resulting from the 50% shortest wavelengths of the spectral power distribution (of the first luminescent material light) into second luminescent material light. In embodiments, the second luminescent material may be configured to convert at most 60%, such as at most 50%, especially at most 40%, of (the spectral power resulting from the shortest wavelengths in the spectral power distribution of) the first luminescent material light received by the second luminescent material into second luminescent material light, though larger numbers are herein not excluded. Additionally or alternatively, the second luminescent material may be configured to convert at least 2%, such as at least 5%, especially at least 10%, of (the spectral power resulting from the shortest wavelengths in the spectral power distribution of) the first luminescent material light received by the second luminescent material into second luminescent material light. In embodiments, a first percentage of the second luminescent material light may thus result from the conversion of light source light, and a second percentage of the second luminescent material light may result from the conversion of first luminescent material light. In embodiments, at least 5%, such as at least 10%, especially at least 25%, like at least 40%, of a spectral power of the second luminescent material light may result from the conversion of first luminescent material light. Additionally or alternatively, at most 70%, such as at most 60%, especially at most 50%, like at most 40%, of the spectral power of the second luminescent material light may result from the conversion of first luminescent 2023PF80238 13 material light. Yet, in (other) embodiments, the second luminescent material may not convert (part of) the first luminescent material light into second luminescent material light, such that the spectral power of the second luminescent material light may result for (essentially) 100% from the conversion of light source light. In embodiments, the second luminescent material light generated by the second luminescent material may especially have a second centroid wavelength λc2. In embodiments, the second centroid wavelength λc2may be selected from the range of 570-650 nm, such as from the range of 580-640 nm, especially from the range of 590-635 nm, like from the range of 590-625 nm. Hence, in embodiments, the second luminescent material may be configured to generate one or more of yellow, orange, and red second luminescent material light. That is, the second luminescent material light may be one or more of yellow light, orange light, and red light. The terms “orange light” or “orange emission”, and similar terms, may especially relate to light having a wavelength in the range of about 590-620 nm. The terms “red light” or “red emission”, and similar terms, may especially relate to light having a wavelength in the range of about 620-780 nm. Additionally or alternatively, in embodiments, the second luminescent material light may have a color point represented by u’ and v’ color coordinates, wherein the u’ and v’ color coordinates indicate a specific color point in the CIE 1976 UCS (uniform chromaticity scale) diagram. In embodiments, the light generating system, such as especially the (solid state) light source(s) and the luminescent converter, or such as especially the LED filament, may be configured such that the u’ color coordinate (or CIE-u’red) may be determined by CIE-u’red≤ c1*[0.5+(0.9538-0.000837*TC)*Pabr], wherein TCis the (selected) correlated color temperature of the system light, and Pabris the factor of the spectral power of the (blue) light source light that is converted by the third luminescent material (see also below). In embodiments, c1 may be selected from the range of 0.75-1.25, such as from the range of 0.80-1.2, especially from the range of 0.9-1.1, like from the range of 0.95-1.05. Additionally or alternatively, in embodiments, TCmay be selected from the range of 1300- 2700 K, such as from the range of 1500-2500 K, especially from the range of 1600-2200 K, like from the range of 1700-2100 K. Further, in embodiments, Pabrmay be selected from the range of ≤ 0.5, such as from the range of ≤ 0.4, especially from the range of ≤ 0.25, like from the range of ≤ 0.1. Additionally or alternatively, Pabrmay be selected from the range of ≥ 0.015, such as from the range of ≥ 0.03, especially from the range of ≥ 0.05, like from the range of ≥ 0.1, such as from the range of ≥ 0.12. Hence, in specific embodiments, Pabr≥ 0.1. Such a value for Pabrmay facilitate that at least 10% of the spectral power of the light source 2023PF80238 14 light may be converted by the third luminescent material. As such, the third luminescent material light may provide a significant contribution to the system light. In (other) embodiments, Pabrmay be selected from the range of 0.015-0.5, such as from the range of 0.03-0.4, especially from the range of 0.05-0.25. Hence, in specific embodiments, the LED filament may be configured such that the following applies: CIE-u’red≤ c1*[0.5+(0.9538- 0.000837*TC)*Pabr], wherein CIE-u’redis the CIE u’ color coordinate of the second luminescent material light, c1 may be selected from the range of 0.9-1.1, TCis the correlated color temperature of the system light, and Pabris the factor of the spectral power of the light source light that is converted by the third luminescent material, wherein TCmay be selected from the range of 1600-2200 K, and wherein Pabrmay be selected from the range of 0.03-0.4. A light generating system, especially a LED filament, wherein the second luminescent material light has a u’ color coordinate selected to be lower than c1*[0.5+(0.9538- 0.000837*TC)*Pabr] may facilitate that the efficiency of the light generating system may be increased, compared to the second luminescent material light has a u’ color coordinate selected to be higher than c1*[0.5+(0.9538-0.000837*TC)*Pabr]. Especially, (a second luminescent material providing) a second luminescent material light having a u’ color coordinate selected to be higher than c1*[0.5+(0.9538- 0.000837*TC)*Pabr] may provide a light generating system generating system light having a higher CRI (especially a higher R9) at a lower efficiency, while (a second luminescent material providing) a second luminescent material light having a u’ color coordinate selected to be lower than c1*[0.5+(0.9538-0.000837*TC)*Pabr] may provide a light generating system generating system light having a lower CRI (especially a lower R9) at a higher efficiency. Hence, the efficiency of the light generating system may be tuned by the choice of second luminescent material (and by the amount of light source light converted by the third luminescent material). In embodiments, CIE-u’redmay especially be (selected from the range of) at least 0.1, such as at least 0.2, especially at least 0.3, like at least 0.4. Hence, in specific embodiments, CIE-u’redmay be at least 0.3. Such a value for CIE-u’redmay provide the benefit that the second luminescent material light may have an intensity in the orange wavelength range. Turning to the third luminescent material, the third luminescent material may comprise one or more luminescent materials of the type M’xM2-2xAX6doped with tetravalent manganese, wherein M’ comprises an alkaline earth cation, M comprises an alkaline cation, and x may be selected from the range of 0-1, wherein A comprises a tetravalent cation, for instance comprising one or more of silicon and titanium, wherein X comprises a monovalent 2023PF80238 15 anion, at least comprising fluorine. Especially, in embodiments, the third luminescent material may comprise a KSiF luminescent material, such as one or more of (K,Rb)2SiF6:Mn4+, (K,Rb)2TiF6:Mn4+, K2(Si,Ti)F6:Mn4+, and Rb2(Si,Ti)F6:Mn4+. Hence, in specific embodiments, the third luminescent material may comprise one or more of (K,Rb)2SiF6:Mn4+, (K,Rb)2TiF6:Mn4+, K2(Si,Ti)F6:Mn4+, and Rb2(Si,Ti)F6:Mn4+. Such luminescent materials may especially provide narrow-band emission in the red wavelength range. Further, such luminescent materials may be relatively efficient. In embodiments, the third luminescent material may be configured to convert at least part of the (blue) light source light received by the third luminescent material into third luminescent material light. Especially, the (blue) light source light may have a spectral power distribution, wherein the light generating system (especially the LED filament) may be configured such that at least 1%, such as at least 2%, especially at least 3%, like at least 5%, of the spectral power of the (blue) light source light may be converted (into third luminescent material light) by the third luminescent material (resulting in a Pabrof ≥ 0.01, ≥ 0.02, ≥ 0.03, and ≥ 0.05, respectively). Additionally or alternatively, the light generating system, especially the LED filament, may be configured such that at most 50%, such as at most 40%, especially at most 30%, of the spectral power of the (blue) light source light may be converted by the third luminescent material. Further, the light generating system, especially the LED filament, may be configured such that at most 20%, such as at most 15%, especially at most 10%, like at most 8% of the spectral power of the (blue) light source light may be converted by the third luminescent material. In embodiments, the LED filament may thus be configured such that between 1-20%, such as between 2-15%, especially between 3-10%, like between 5-8%, of the spectral power of the blue light source light may be converted by the third luminescent material. Hence, in specific embodiments, the blue light source light may have a spectral power distribution, wherein the LED filament may be configured such that between 3-10% of the spectral power of the blue light source light may be converted by the third luminescent material. Such a percentage (range) of the spectral power converted by the third luminescent material may provide the benefit that filament (or system) light having a desired CCT may be provided at higher efficiencies. Further, such a percentage (range) may facilitate that the value for CIE-u’redmay be closer to 0.5, facilitating the selection of a second luminescent material configured to provide orange-red second luminescent material light. In embodiments, the third luminescent material light (generated by the third luminescent material) may have a third centroid wavelength λc3. In embodiments, the third 2023PF80238 16 centroid wavelength λc3may be selected from the range of 605-650 nm, such as from the range of 610-645 nm, especially from the range of 615-640 nm, like from the range of 620- 635 nm. Hence, in embodiments, the third luminescent material may be configured to generate red third luminescent material light. That is, the third luminescent material light may especially be red light. In embodiments, the light generating system may be configured to generate system light. The system light may in embodiments especially comprise (one or more of) the first luminescent material light, the second luminescent material light, and the third luminescent material light. Further, in embodiments, the system light may have a spectral power distribution. Especially, the system light may have a spectral power distribution in the (visible) wavelength range of 380-780 nm. Hence, in embodiments, the system light may be visible light. In embodiments, system light may (essentially) not comprise the light source light, i.e., in embodiments, the system light may be (essentially) free from (blue) light source light. Alternatively, the system light may comprise at least part of the (blue) light source light. Especially, in embodiments, the system light may comprise at least 0.01%, such as at least 0.05%, especially at least 0.1%, like at least 0.5%, of the spectral power of the light source light emitted by the (solid state) light sources. Additionally or alternatively, the system light may comprise at most 20%, such as at most 15%, especially at most 12%, like at most 10%, of the spectral power of the light source light emitted by the (solid state) light sources. Hence, in embodiments, the system light may have some intensity (or spectral power) in the (blue) wavelength range of 380-490 nm. Especially, in embodiments, the system light may have a spectral power distribution in the wavelength range of 380-780 nm, wherein selected from the range of 0.01-20%, such as from the range of 0.05-15%, especially from the range of 0.1-12%, like from the range of 0.5-10%, of the spectral power may be in the 380-490 wavelength range. Hence, in specific embodiments, the system light may have a spectral power distribution in the wavelength range of 380-780 nm, wherein selected from the range of 0.1-12% of the spectral power may be in the 380-490 nm wavelength range. Such a spectral power distribution of the system light may provide system light having a correlated color temperature selected from the range of ≤ 2700 K, such as from the range of ≤ 2500 K. Further, system light having at least some intensity in the wavelength range of 380- 490 nm may provide the benefit that such system light may have a color rendering index of ≥ 60. In embodiments, the system light may be white light. The term “white light”, and similar terms, herein, is known to the person skilled in the art. It may especially relate to 2023PF80238 17 light having a correlated color temperature (CCT) between about 1600 K and 20000 K, such as between 2000 and 20000 K, especially between 2700 and 20000 K, for general lighting especially in the range of about 1600-7000 K, such as in the range of 2000-6500 K. In embodiments, the correlated color temperature (CCT) is especially within about 15 SDCM (standard deviation of color matching) from the BBL (black body locus), especially within about 10 SDCM from the BBL, even more especially within about 5 SDCM from the BBL. In embodiments, the system light may be white light having a CCT selected from the range of at maximum 2700 K, such as at maximum 2500 K, especially at maximum 2200 K. Additionally or alternatively, the system light may be white light having a CCT selected from the range of at least 1400 K, such as at least 1500 K, especially at least 1600 K. Further, in embodiments, the system light may have a color rendering index (CRI) selected from the range of ≥ 60, such as from the range of ≥ 62, especially from the range of ≥ 65, like from the range of ≥ 70. Additionally or alternatively, the system light may have a CRI selected from the range of ≤ 85, such as from the range of ≤ 80, especially from the range of ≤ 78, like from the range of ≤ 75. In embodiments, the light generating system may generate the system light with a luminous efficacy of radiation (in lumens per optical Watt). Here, the term “luminous efficacy of radiation” especially refers to the (amount of) lumens (of the system light) generated by the light generating system per Watt of the blue light source light (and may therefore be related to a conversion efficiency of the luminescent converter). In embodiments, the luminous efficacy of radiation of the light generating system may be selected from the range of ≥ 235 Lm / Wopt, such as from the range of ≥ 240 Lm / Wopt, especially from the range of ≥ 245 Lm / Wopt, like from the range of ≥ 250 Lm / Wopt. Hence, in specific embodiments, the light generating system(, especially the LED filament,) may be configured to generate system light with a luminous efficacy selected from the range of ≥ 245 Lm / Wopt, wherein the system light may have a CCT of at maximum 2500 K and a CRI selected from the range of ≥ 70. Such a light generating system, especially such a LED filament, may thus be configured to provide (white) system light at an improved luminous efficacy compared to prior art systems. Hence, in embodiments, the invention may provide an efficient warm white LED filament. As indicated above, the light generating system may comprise a LED filament. In (such) embodiments, the luminescent converter may especially be configured as an encapsulant covering the solid state light source (configured on an elongated carrier). Hence, in embodiments, the light generating system may comprise a LED filament comprising the luminescent converter (as an encapsulant). LED filaments as such are known, and are e.g. 2023PF80238 18 described in US 8,400,051 B2, WO2020016058, WO2019197394, etc., which are herein incorporated by reference. In general, a LED filament may in embodiments comprise (i) a plurality of solid state light sources, such as a plurality of light emitting diodes (LEDs), arranged on (at least a first major surface of) an elongated carrier, and (ii) an (elongated) encapsulant covering the plurality of LEDs and at least part of the elongated carrier. The LED filament may in embodiments be defined by a filament length LF, a filament width WF, and a filament thickness TF. The LED filament may further comprise a filament axis of elongation AF. The filament axis of elongation AFmay especially be a straight axis centered on the direction along which the LED filament is elongated. The filament axis of elongation AFmay define an axis length LA, wherein the axis length LAmay be the length of the LED filament along the filament axis of elongation AF. In some embodiments, the LED filament may be straight. In straight embodiments, the filament length LFmay (essentially) be equivalent to the axis length LA. In other embodiments, the LED filament may be curved. For instance, the filament may have a (2D or 3D) spiraling shape, (like) a helical shape, or another curved shape. In curved embodiments, the axis length LAmay be smaller than the filament length LF, such as LA / LF≤ 0.95, especially LA / LF≤ 0.75, more especially LA / LF≤ 0.55. Further, the LED filament may have relatively high aspect ratios (LF / WFor LF / TF), such as at least 10, especially at least 15, such as at least 20, more especially at least 50. Large aspect ratios may better mimic a filament. Yet, in embodiments, the aspect ratio (LF / WFand / or LF / TF) may be at most 900, such as at most 650, especially at most 500. Hence, in specific embodiments, 10*WF≤ LF≤ 900*WF, and 10*TF≤ LF≤ 900*TF. Further, as indicated, the LED filament may comprise an elongated carrier, solid state light sources, and an encapsulant. Especially, the elongated carrier may support the solid state light sources. The elongated carrier may e.g. comprise glass, quartz, metal, or sapphire. In other embodiments, the elongated carrier may e.g. comprise a polymeric material or (flexible) metal, e.g., a film or foil. The elongated carrier may be rigid (self-supporting), but may (in polymeric embodiments) also be flexible. In embodiments, the elongated carrier may be light transmissive, translucent, or transparent for light, especially visible light. Especially, in embodiments, the elongated carrier may be transmissive for light, such as transmissive for one or more (especially all) of the first luminescent material light, the second luminescent material light, and the third luminescent material light. Further, the elongated carrier may be transmissive for the light source light. Hence, in specific embodiments, the elongated carrier may be transmissive for one or more of the light source light, the first luminescent material light, the second luminescent material light, and the third luminescent 2023PF80238 19 material light. Alternatively, in embodiments, the elongated carrier may be light reflective, such as especially reflective for one or more of the light source light, the first luminescent material light, the second luminescent material light, and the third luminescent material light, such as reflective for at least the light source light. In specific embodiments, the carrier may be diffuse reflective. The elongated carrier may have (essentially) similar dimensions to the LED filament. Especially, the elongated carrier may (essentially) define the filament length LFand axis length LAof the LED filament. The width WFand thickness TFof the LED filament may be defined by the elongated carrier as well as other components of the LED filament, e.g., the solid state light sources and the encapsulant. In embodiments, the (elongated) carrier may comprise a first major surface at a first side of the carrier and a second major surface at a second side of the carrier, opposite to the first side. In embodiments, the solid state light sources may be arranged on at least one of these surfaces. Hence, in embodiments, at least part of, such as all of, the solid state light sources may be mounted onto the first major surface. Additionally or alternatively, at least part of the solid state light sources may be mounted onto the second major surface. Hence, in embodiments, the solid state light sources may be arranged, mounted and / or mechanically coupled on / to the carrier, wherein the carrier may especially be configured to mechanically and / or electrically support the LEDs. In embodiments, the solid state light sources may comprise LEDs. Alternatively or additionally, in embodiments, the solid state light sources may comprise diode lasers. Further, the LED filament may comprise one or more of LEDs, laser diodes, superluminescent diodes, and multi-junction diodes. Especially, the LED filament comprises a plurality of light emitting diodes (LEDs). The (plurality of) solid state light sources may be arranged in an array (on the elongated carrier), especially over (at least part of) the filament length LF. The number of solid state light sources in the array may be at least 4, such as at least 8, even more especially at least 12, and may e.g. be up to 100, or yet even larger. Especially, in embodiments the number of solid state light sources in the array may be selected from the range of 10-2000, such as from the range of 10-1500, especially from the range of 10-1000. In embodiments, the solid state light sources may be configured in a 1D (linear) array over at least part of the filament length LF. A first and a last solid state light source may, when measured along the LED filament, have a mutual distance of at least 0.5*LF, even more especially at least 0.7*LF. Further, in embodiments, the solid state light sources may be configured in two 1D arrays, one on the first major surface of the elongated carrier and one on the second major surface. A 2D array of solid state light sources of n*m 2023PF80238 20 LEDs may also be possible. In embodiments, n may be selected from the range of 1-4, such as 1-3, like 1-2, such as in embodiments 1 or in embodiments 2, and m may be selected from the range of larger than n, such as especially selected from the range of at least 4 (when n<4), like at least 6, such as at least 8. Hence, a 2D array of solid state light sources may especially have a (much) smaller number of rows (n) than the number of solid state light sources in those respective rows (m), such as n / m ≤0.2, like n / m ≤0.1, especially n / m ≤0.05. In embodiments, the LED filament may comprise an encapsulant. The encapsulant may especially cover (at least some of) the plurality of solid state light sources. Further, the encapsulant may cover at least part of the elongated carrier, such as at least (part of) one of the first major and second major surface. In general, the encapsulant may be in contact with the elongated carrier and may cover all of the solid state light sources. Hence, in embodiments the encapsulant may be configured over a substantial part of the filament length LFof the LED filament (such as over more than 70% of the filament length LF). The encapsulant may be a continuous coating along the filament length LF, at one or both of the first major and the second major surface. Further, the encapsulant may at least partly cover the solid state light sources, such as in embodiments at least 50% of the total number of solid state light sources in the array, such as at least 75%, especially at least 95%, up to 100%. Herein, the phrase “the encapsulant encloses at least part of the solid state light source”, and similar phrases, especially indicate that at least part of the light emitting surface may be enclosed by the encapsulant. The encapsulant may comprise a polymer material, which may in embodiments be flexible, such as for example a silicone. In (other) embodiments, the encapsulant may comprise a resin. As indicated above, the (elongated) encapsulant may comprise the luminescent converter. Additionally or alternatively, the luminescent converter may be an encapsulant, or may be configured as an encapsulant in the LED filament. Hence, in embodiments, the encapsulant may comprise one or more (such as especially all) of the first luminescent material, the second luminescent material, and the third luminescent material. Especially, the encapsulant may comprise the first, second, and third luminescent materials in a combined (or total) luminescent material concentration Cl,c. In embodiments, the combined luminescent material concentration Cl,cmay be selected from the range of ≥ 1 v / v / %, such as from the range of ≥ 2 v / v%, especially from the range of ≥ 3 v / v%, like from the range of ≥ 5 v / v%. That is, the combined volume of the first luminescent material, second luminescent material, and third luminescent material may be ≥ 1%, such as ≥ 2%, especially ≥ 3%, like ≥ 5%, of the total volume of the luminescent converter and / or encapsulant comprising said 2023PF80238 21 luminescent materials. Additionally or alternatively, the combined luminescent material concentration Cl,cmay be selected from the range of ≤ 50 v / v / %, such as from the range of ≤ 40 v / v%, especially from the range of ≤ 30 v / v%, like from the range of ≤ 25 v / v%. Further, the combined luminescent material concentration Cl,cmay be selected from the range of 1-50 v / v / %, such as from the range of 2-40 v / v%, especially from the range of 3-30 v / v%, like from the range of 5-25 v / v%. Hence, in specific embodiments, the encapsulant may comprise the first luminescent material, second luminescent material, and third luminescent material in a combined luminescent material concentration Cl,c, wherein the combined luminescent material concentration Cl,cmay be selected from the range of 3-30 v / v%. Such a combined luminescent material concentration Cl,cmay be high enough to allow the luminescent material to convert most of the light source light, yet may be low enough to optionally allow some of the light source light to be transmitted through the encapsulant and / or luminescent converter. Further, such a combined luminescent material concentration Cl,cmay be low enough to prevent or reduce absorption of e.g. first luminescent material light by the second luminescent material within the luminescent converter and / or encapsulant. In embodiments, the encapsulant may further comprise a light scattering material. The light scattering material may especially be configured embedded in the encapsulant, e.g. in the (flexible) polymer material and / or the resin. Further, in embodiments, the light scattering material may be configured to scatter (or “diffuse”) the light source light, especially in a direction transverse to a normal of the (first and / or second) major surface. In specific embodiments, the light scattering material may comprise light scattering particles, such as e.g. at least one of BaSO4, A12O3and TiO2particles. Yet, in embodiments, the encapsulant may not comprise the light scattering material. In (such) embodiments, the LED filament may comprise a second encapsulant, wherein the second encapsulant may comprise the light scattering material. The second encapsulant may be configured on top of (and in physical contact with) the (first) encapsulant. Further, the second encapsulant may be configured to cover at least part of the (first) encapsulant. Especially, the second encapsulant may be configured to cover at least 50%, such as at least 65%, especially at least 80%, like at least 90%, including (essentially) 100%, of the (first) encapsulant. Further, in embodiments, the second encapsulant may comprise one or more of a (flexible) polymer material (e.g. a silicone) and a resin, in which the light scattering material may be embedded. In embodiments, the second encapsulant may be (diffuse) transmissive for one or more of the light source light, the first luminescent material light, the second luminescent material light, and the third luminescent material light, such as especially for all of the light source light and 2023PF80238 22 the first, second, and third luminescent material light. Especially, the second encapsulant may be configured to transmit ≥ 70%, such as ≥ 85%, especially ≥ 90%, like ≥ 95%, including (essentially) 100%, of the light source light and first, second, and third luminescent material light incident on the second encapsulant. Hence, in specific embodiments, the LED filament may further comprise a second encapsulant, wherein the second encapsulant may be configured to cover at least part of the encapsulant, and wherein the second encapsulant may comprise a light scattering material. A second encapsulant comprising a light scattering material may provide the benefit that the light source light and the (first, second, and third) luminescent material light may be diffused upon transmission through the second encapsulant. Further, a second encapsulant comprising a (white) light scattering material may provide an opaque appearance of the LED filament, especially of the second encapsulant, in an off-state of the light generating system. In embodiments, the second encapsulant may (further) be configured to scatter (artificial and / or natural) daylight incident on the second encapsulant. Especially, in embodiments, the second encapsulant may be configured to scatter blue (artificial and / or natural) daylight, thereby preventing at least part of said blue light from being incident on the (first) encapsulant comprising the luminescent materials. In embodiments, the first encapsulant may be configured to absorb blue light in an off-state (or non-operational mode) of the LED filament, thereby facilitating a (yellow-orange) colored appearance of the first encapsulant. Hence, by scattering (and partially reflecting) the blue (artificial and / or natural) daylight (in the off-state), a white or whitish appearance of the LED filament, especially of the second encapsulant, may be provided in the non-operational mode of the LED filament. Here, the term “whitish” may refer to an off-white color, a shade of white, yet also to (pure) white. Examples of “whitish” colors may be pure white, cream, eggshell, ivory, Navajo white, and vanilla. Such a whitish appearance may be more decorative than a (non-white) colored (e.g. yellow) appearance. In embodiments, a light scattering material in the second encapsulant may be white. In embodiments, the LED filament may be configured to generate filament light, which may comprise one or more of (scattered) light source light and first, second, and third luminescent material light. The term “LED filament light” may refer to the light emitted by the LED filament during operation of the LED filament. In embodiments, the filament light may at least comprise light at a wavelength selected from the range of 380-780 nm, i.e., visible light. Further, in embodiments, the filament light may be white light having a CCT selected from the range of 1500-3000 K, such as especially from the range of 1500-2500 K. 2023PF80238 23 Hence, the filament light may be relatively warm (white) light. In embodiments, the system light may comprise the filament light. Further, the solid state light sources, comprised by the LED filament (or by the light generating system), may be configured to generate light source light. In embodiments, at least two, such as all, of the solid state light sources may be configured to provide light source light having essentially the same spectral power distribution. In other embodiments, at least two, such as all, of the solid state light sources may be configured to emit light source light having different spectral power distributions. Especially, in embodiments, the light generating system, especially the LED filament, may comprise second (solid state) light sources. In embodiments, the light generating system, especially the LED filament, may comprise 1-1000, such as from the range of 2-750, especially from the range of 5-500, like from the range of 10-200, second (solid state) light sources. The second (solid state) light sources may be configured to generate second light source light. In embodiments, the second light source light may have a different spectral power distribution than the (first) light source light. Especially, the second light source light may have a second peak wavelength λp2, differing from the (first) peak wavelength λp1of the (first) light source light. In embodiments, the second peak wavelength λp2may be selected from the range of 380-490 nm, such as from the range of 400-480 nm, especially from the range of 420-470 nm, like from the range of 440-465 nm. Hence, in embodiments, the second light source light may be one or more of violet light and blue light, such as especially blue light. Further, in embodiments, |λp2-λp1| ≥ 5 nm, such as |λp2-λp1| ≥ 10 nm, especially |λp2-λp1| ≥ 20 nm, like |λp2-λp1| ≥ 30 nm. Additionally or alternatively, in embodiments, |λp2-λp1| ≤ 100 nm, such as |λp2-λp1| ≤ 75 nm, especially |λp2-λp1| ≤ 50 nm, like |λp2-λp1| ≤ 40 nm. In embodiments, the luminescent converter (especially the first, second, and third luminescent materials) of the light generating system or of the LED filament (wherein the luminescent converter may further be referred to as encapsulant) may be configured such that at least part of the second light source light received by the luminescent converter may be converted into (first, second, and third) luminescent material light. Hence, in embodiments, the light generating system, especially the LED filament, may be configured such that between 3-70%, such as between 5-60%, especially between 10-50%, of the spectral power of the (blue) second light source light may be converted by the first luminescent material. In embodiments, the percentage of (the spectral power of) the second light source light converted by the first luminescent material may be the same as the percentage of the (first) light source light converted by the first luminescent material. Yet, in 2023PF80238 24 embodiments, the percentage of the second light source light converted by the first luminescent material may be different from the percentage of the (first) light source light converted by the first luminescent material. Similarly, the light generating system, especially the LED filament, may be configured such that between 3-50%, such as between 5-40%, especially between 10-30%, of the spectral power of the (blue) second light source light may be converted by the second luminescent material (wherein this percentage may be the same or different as the percentage of the spectral power of the (first) light source light converted by the second luminescent material). Additionally or alternatively, the light generating system, especially the LED filament, may be configured such that between 1-20%, such as between 2-15%, especially between 3-10%, like between 5-8%, of the spectral power of the (blue) second light source light may be converted by the third luminescent material (wherein this percentage may be the same or different as the percentage of the spectral power of the (first) light source light converted by the third luminescent material). Hence, in embodiments, a combined (first, second, and third) luminescent material light generated in response to irradiation with the second light source light may have a different spectral power distribution (and / or CCT, and / or CRI) than a combined (first, second, and third) luminescent material light generated in response to irradiation with the (first) light source light. In embodiments, the light generating system may comprise the LED filament, and the second light sources may (also) be configured on the elongated carrier (of the LED filament). Hence, in embodiments, the second light sources may especially be selected from the group of LEDs, laser diodes, superluminescent diodes, and multi-junction diodes. In embodiments, the (first) light sources may be configured on the first major surface of the elongated carrier, and the second light sources may be configured on the second major surface of the elongated carrier. Alternatively, both the (first) light sources and the second light sources may be configured on one of the first and second major surfaces. In (other) embodiments, both the first and second light sources may be configured on both the first and second major surfaces of the elongated carrier (wherein the first and second light sources may optionally be mixed and / or randomly distributed). Hence, in embodiments, the filament light may comprise (at least part of) the second light source light. Additionally or alternatively, the system light may comprise (at least part of) the second light source light. In embodiments, the (first) light sources and the second light sources may be separately controllable. That is, in embodiments, the (first) light sources may be controlled independently from the second light sources. Additionally or alternatively, in embodiments, all of the (first and second) light sources may be configured individually controllable. In 2023PF80238 25 (other) embodiments, the (first) light sources and second light sources may each comprise subsets of one or more light sources, wherein the subsets of one or more light sources may be individually controlled. Hence, in embodiments, the light generating system may comprise a control system. The control system may be configured to control the (first) light sources and the second light sources. Further, in embodiments, the control system may be configured to control a spectral power distribution of the system light (and / or of the filament light), especially by controlling the (first) light sources and the second light sources. For instance, as indicated above, the spectral power distribution of the combined (first, second, and third) luminescent material light upon irradiation with either (first) light source light or second light source light may differ, thereby providing system light having a different spectral power distribution. Hence, in specific embodiments, the light generating system may further comprise a control system and second light sources, wherein the second light sources may be configured on the elongated carrier, wherein the encapsulant may cover the second light sources, wherein the second light sources may be configured to generate blue second light source light having a second peak wavelength differing from a peak wavelength of the light source light, and wherein the control system may be configured to control a spectral power distribution of the system light by controlling the light sources and the second light sources. A light generating system comprising a control system and second light sources may thus facilitate controlling the spectral power distribution of the system light. Especially, with such a light generating system, only one LED filament may be needed to allow control over the spectral power distribution of the system light, providing a compact and relatively simple tunable light generating system. The term “controlling” and similar terms especially refer at least to determining the behavior or supervising the running of an element. Hence, herein “controlling” and similar terms may e.g. refer to imposing behavior on the element, such as e.g. measuring, displaying, actuating, opening, shifting, changing temperature, etc.. Beyond that, the term “controlling” and similar terms may additionally include monitoring. Hence, the term “controlling” and similar terms may include imposing behavior on an element and monitoring the element. The controlling of the element can be done with a control system, which may also be indicated as “controller”. The control system and the element may thus at least temporarily, or permanently, functionally be coupled. The element may comprise the control system. In embodiments, the control system and element may not be physically coupled. Control can be done via wired and / or wireless control. The term “control system” may also refer to a plurality of different control systems, which especially are functionally 2023PF80238 26 coupled, and of which e.g. one control system may be a master control system and one or more others may be slave control systems. A control system may comprise or may be functionally coupled to a user interface. The control system may also be configured to receive and execute instructions from a remote control. In embodiments, the control system may be controlled via an App on a device, such as a portable device, like a Smartphone or I- phone, a tablet, etc.. The device is thus not necessarily coupled to the lighting system, but may be (temporarily) functionally coupled to the lighting system. In such embodiments the control system of the lighting system may be a slave control system or control in a slave mode. The lighting system may also comprise means for communicating with other systems or devices, such as on the basis of Bluetooth, Thread, WIFI, LiFi, ZigBee, BLE or WiMAX, or another wireless technology. The system, or apparatus, or device may execute an action in a “mode” or “operational mode”. The term “operational mode” may also be indicated as “controlling mode”. Likewise, in a method an action or stage, or step may be executed in a “mode” or “operational mode”. This does not exclude that the system, or apparatus, or device may also be adapted for providing another controlling mode, or a plurality of other controlling modes. Likewise, this may not exclude that before executing the mode and / or after executing the mode one or more other modes may be executed. However, in embodiments a control system may be available, that is adapted to provide at least the controlling mode. Would other modes be available, the choice of such modes may especially be executed via a user interface, though other options, like executing a mode in dependence of a sensor signal or a (time) scheme, may also be possible. Hence, in embodiments, the control system may control in dependence of one or more of an input signal of a user interface, a sensor signal (of a sensor), and a timer. The term “timer” may refer to a clock and / or a predetermined time scheme. The operational mode may in embodiments also refer to a system, or apparatus, or device, that can only operate in a single operational mode (i.e. “on”, without further tunability). As indicated above, the spectral power distribution of the system light may be controlled by (independently) controlling the (first) light sources and the second light sources (comprised by the same LED filament). Additionally or alternatively, the spectral power distribution of the system light may be controlled by (independently) controlling different LED filaments (and / or different sets of light sources and luminescent converters). Hence, in embodiments, the light generating system may (further) comprise a second LED filament. For ease of distinguishing the LED filament and the second LED filament, the LED filament described above may hereafter also be referred to as “first LED filament”. In embodiments, 2023PF80238 27 the (first) LED filament and second LED filament may (both) comprise the same (first) light sources (and optionally the same second light sources). Alternatively, the (first) LED filament may comprise the (first) light sources, and the second LED filament may comprise the second light sources. Further, in embodiments, both the (first) LED filament and second LED filament may (each) comprise an encapsulant comprising a luminescent converter. Hence, the (first) LED filament may comprise a first luminescent converter (configured as the encapsulant of the (first) LED filament), and the second LED filament may comprise a second luminescent converter (configured as the encapsulant of the second LED filament). In embodiments, the first luminescent converter may be (essentially) identical to the second luminescent converter. Alternatively, the first luminescent converter may be different from the second luminescent converter. Especially, the (first luminescent converter of the) first LED filament and the (second luminescent converter of the) second LED filament may differ in relative amount (i.e., composition) of the (first, second, and third) luminescent materials. Additionally or alternatively, the (first) LED filament and the second LED filament may differ in the combined luminescent material concentration Cl,c. In embodiments, the (first) LED filament and the second LED filament may be configured to generate (respectively) (first) filament light and second filament light, wherein the (first) filament light and second filament light may differ in spectral power distribution. Additionally or alternatively, the (first) filament light and the second filament light may differ in correlated color temperature (CCT). In embodiments, the (first) filament light and the second filament light may (each) have a CCT individually selected from the range of 1300-2700 K, such as from the range of 1500-2500 K, especially from the range of 1600- 2200 K, like from the range of 1700-2100 K. Alternatively, one of the (first) LED filament and the second LED filament may be configured to generate (white) filament light having a CCT selected from the range of 1300-2700 K, and the other of the (first) LED filament and the second LED filament may be configured to generate colored light. Hence, in embodiments, the system light (comprising the (first) filament light and the second filament light) may be colored light. In embodiments, the control system may be configured to control the (first) LED filament and the second LED filament, such as especially the (first and optionally second) light sources comprised by the (first) LED filament and the second LED filament. Further, the control system may be configured to control a spectral power distribution (especially a CCT) of the system light by controlling the (first) light sources comprised by the (first) LED filament and the (first) light sources comprised by the second LED filament. 2023PF80238 28 In embodiment, the control system may be configured to switch off the second LED filament, such that the system light may (comprise, such as) be based only on the ((first) filament light of the) (first) LED filament. In such embodiments, the system light may especially have a first correlated color temperature TC1. Additionally or alternatively, in embodiments, the control system may be configured to switch off the (first) LED filament, such that the system light may (comprise, such as) be based only on the (second filament light of the) second LED filament. In such embodiments, the system light may especially have a second correlated color temperature TC2. In embodiments |TC1-TC2| ≥ 200 K, such as |TC1-TC2| ≥ 500 K, especially |TC1-TC2| ≥ 1000 K, like |TC1-TC2| ≥ 1500 K. Additionally or alternatively, in embodiments, |TC1-TC2| ≤ 3000 K, such as |TC1-TC2| ≤ 2500 K, especially |TC1-TC2| ≤ 2000 K, like |TC1-TC2| ≤ 1500 K. Hence, in specific embodiments, the light generating system may further comprise a second LED filament, wherein the LED filament and the second LED filament may differ in relative amounts of the luminescent materials; wherein the system light based on the LED filament only may have a first correlated color temperature TC1and wherein the system light based on the second LED filament only may have a second correlated color temperature TC2, wherein |TC1-TC2| ≥ 1000 K; and wherein the control system may be configured to control a spectral power distribution of the system light by controlling the light sources comprised by the LED filament and the light sources comprised the second LED filament. A light generating system comprising the (first) LED filament and the second LED filament may provide the benefit that the CCT of the system light may be controlled (and / or adjusted) over a larger range. Hence, such a light generating system may provide more options for consumers, and may provide a more decorative effect. Further, in embodiments, one of the (first) LED filament and the second LED filament may be configured to generate filament light having a relatively lower CRI at a higher efficiency, while the other of the (first) LED filament and the second LED filament may be configured to generate filament light having a relatively higher CRI at a lower efficiency. By combining both LED filaments within the same light generating system, a consumer may be able to adjust the light based on their requirements throughout the day (good CRI for light-sensitive work, or high efficiency for reducing energy consumption). In embodiments, the light generating system may further comprise one or more additional LED filaments. In embodiments, the one or more additional LED filaments may each comprise (solid state) light sources and a luminescent converter differing in the relative amounts of the first, second, and third luminescent material (compared to the (first) LED filament and the second LED filament). Further, in embodiments, the one or more 2023PF80238 29 additional LED filaments may each comprise a luminescent converter differing in the type of luminescent materials comprised by the luminescent converter. In embodiments, the one or more additional LED filaments may be configured to generate white light. Additionally or alternatively, in embodiments, the one or more additional LED filaments may be configured to generate colored light. Returning to the light sources, here below some general embodiments relating to the (first) (solid state) light sources and the second light sources are provided. The term “light source” may in principle relate to any light source known in the art. In a specific embodiment, the light source comprises a solid state light source (such as an LED or laser diode (or “diode laser”)). The term “light source” may also relate to a plurality of (essentially identical (or different)) light sources, such as 2-2000 (solid state) (LED) light sources. The phrases “different light sources” or “a plurality of different light sources”, and similar phrases, may in embodiments refer to a plurality of solid-state light sources selected from at least two different bins. Likewise, the phrases “identical light sources” or “a plurality of same light sources”, and similar phrases, may in embodiments refer to a plurality of solid-state light sources selected from the same bin. Hence, the term LED may also refer to a plurality of LEDs. Further, the term “light source” may in embodiments also refer to a so-called chip-on- board (COB) light source. The term “COB” especially refers to LED chips in the form of a semiconductor chip that is neither encased nor connected but directly mounted onto a substrate, such as a PCB. Hence, a plurality of light emitting semiconductor light source may be configured on the same substrate. In embodiments, a COB is a multi LED chip configured together as a single lighting module. The term “light source” may also refer to a chip scale package (CSP) and / or a chip scale packaged (CSP) LED. A CSP may comprise a single solid state die (such as a LED) with provided thereon a luminescent material comprising layer. The term “light source” may also refer to a midpower package. A midpower package may comprise one or more solid state die(s). The die(s) may be covered by a luminescent material comprising layer. The die dimensions may be equal to or smaller than 2 mm, such as in the range of e.g. 0.2-2 mm. Herein, the term “light source” may also especially refer to a small solid state light source, such as having a mini size or micro size. For instance, the light sources may comprise one or more of mini LEDs and micro LEDs, such as especially micro LEDs or “microLEDs” or “µLEDs”. Herein, the term mini size or mini LED especially refers to solid state light sources having dimensions, such as die dimension, especially length and width, selected from the range of 100 µm – 1 mm. Herein, the term µ size or micro LED especially refers to solid 2023PF80238 30 state light sources having dimensions, such as die dimension, especially length and width, selected from the range of 100 µm and smaller. The term “light source” may refer to a semiconductor light-emitting device, such as a light emitting diode (LEDs), a resonant cavity light emitting diode (RCLED), a vertical cavity laser diode (VCSELs), an edge emitting laser, etc. The term “light source” may also refer to an organic light-emitting diode (OLED), such as a passive-matrix (PMOLED) or an active-matrix (AMOLED). In an embodiment, the light source comprises an LED. The terms “light source” or “solid state light source” may also refer to a superluminescent diode (SLED). Especially, the term “solid state light source”, or “solid state material light source”, and similar terms, may refer to semiconductor light sources, such as a light emitting diode (LED), a laser diode, a superluminescent diode, or a multi-junction diode. In embodiments, the light source may comprise one or more micro-optical elements (array of micro lenses) downstream of a single solid-state light source, such as an LED, or downstream of a plurality of solid-state light sources (i.e. e.g. shared by multiple LEDs). In embodiments, the light source may comprise an LED with on-chip optics. In embodiments, the light source comprises pixelated single LEDs (with or without optics) (offering in embodiments on-chip beam steering). In embodiments, the light source may be configured to provide primary radiation, which is used as such, such as e.g. a blue light source, like a blue LED, or a green light source, such as a green LED, and a red light source, such as a red LED. Such LEDs, which may not comprise a luminescent material (“phosphor”) may be indicated as direct color LEDs. In other embodiments, however, the light source may be configured to provide primary radiation and part of the primary radiation is converted into secondary radiation. Secondary radiation may be based on conversion by a luminescent material. The secondary radiation may therefore also be indicated as luminescent material radiation. The luminescent material may in embodiments be comprised by the light source, such as an LED with a luminescent material layer or dome comprising luminescent material. Such LEDs may be indicated as phosphor converted LEDs or PC LEDs (phosphor converted LEDs). In other embodiments, the luminescent material may be configured at some distance (“remote”) from the light source, such as an LED with a luminescent material layer not in physical contact with a die of the LED. In embodiments, the light generating system may comprise a luminescent converter (optionally configured as an encapsulant of a LED filament). In embodiments, the light generating system may comprise a PC LED. In other embodiments, the light generating 2023PF80238 31 system may comprise a direct LED (i.e. no phosphor). In embodiments, the light generating system may comprise a laser device, like a laser diode. In embodiments, the light generating system may comprise a superluminescent diode. Hence, in specific embodiments, the light source may be selected from the group of laser diodes and superluminescent diodes. In other embodiments, the light source may comprise an LED. The light source may especially be configured to generate light source light having an optical axis (O), (a beam shape,) and a spectral power distribution. The light source light may in embodiments comprise one or more bands, having band widths as known for lasers. The term “light source” may (thus) refer to a light generating element as such, like e.g. a solid state light source, or e.g. to a package of the light generating element, such as a solid state light source, and one or more of a luminescent material comprising element and (other) optics, like a lens, a collimator. In embodiments, the term “light source” may thus also refer to a combination of a light source, like an LED, and an optical filter, which may change the spectral power distribution of the light generated by the light source. Especially, the term “light generating device” may be used to address a light source and further (optical components), like an optical filter and / or a beam shaping element, etc. Further, the term “light source” may (thus) in embodiments also refer to a light source that is (also) based on conversion of light, such as a light source in combination with a luminescent converter material. A light converter element (“converter element” or “converter”) may comprise a luminescent material comprising element. For instance, a solid state light source as such, like a blue LED, is a light source. A combination of a solid state light source (as light generating element) and a light converter element, such as a blue LED and a light converter element, optically coupled to the solid state light source, may also be a light source (but may also be indicated as light generating device). Hence, a white LED is a light source (but may e.g. also be indicated as (white) light generating device). The term “laser light source” especially refers to a laser. Such laser may especially be configured to generate laser light source light having one or more wavelengths in the UV, visible, or infrared, especially having a wavelength selected from the spectral wavelength range of 200-2000 nm, such as from the spectral wavelength range of 300-1500 nm. The term “laser” especially refers to a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. Especially, in embodiments the term “laser” may refer to a solid-state laser. In specific embodiments, the terms “laser” or “laser light source”, or similar terms, may refer to a laser diode (or diode laser). Hence, in embodiments the light source comprises a laser light source. In 2023PF80238 32 embodiments, the terms “laser” or “solid state laser” or “solid state material laser” may refer to one or more of a semiconductor laser diodes, such as GaN, InGaN, AlGaInP, AlGaAs, InGaAsP, lead salt, vertical cavity surface emitting laser (VCSEL), quantum cascade laser, hybrid silicon laser, etc. The term “solid state material laser”, and similar terms, may thus refer to a solid state laser like based on a crystalline or glass body dopes with ions, like transition metal ions and / or lanthanide ions, to a fiber laser, to a photonic crystal laser, to a semiconductor laser, etc. A laser may be combined with an upconverter in order to arrive at shorter (laser) wavelengths. For instance, with some (trivalent) rare earth ions upconversion may be obtained or with non-linear crystals upconversion can be obtained. Alternatively, a laser can be combined with a downconverter, such as a dye laser, to arrive at longer (laser) wavelengths. In embodiments, the term “laser light source” may also refer to a plurality of (different or identical) laser light sources. In specific embodiments, the term “laser light source” may refer to a plurality N of (identical) laser light sources. In embodiments, N≥2, such as N≥5, especially N≥8. In this way, a higher brightness (of the laser light) may be obtained. In embodiments, laser light sources may be arranged in a laser bank. The laser bank may in embodiments comprise heat sinking and / or optics (e.g. a lens to collimate the laser light). Hence, in embodiments lasers in a laser bank (or “laser array bank”) may share the same optics. The laser light source is configured to generate laser light source light (or “laser light”). The light source light may essentially consist of the laser light source light. The light source light may also comprise laser light source light of two or more (different or identical) laser light sources. For instance, the laser light source light of two or more (different or identical) laser light sources may be coupled into a light guide, to provide a single beam of light comprising the laser light source light of the two or more (different or identical) laser light sources. In specific embodiments, the light source light is thus especially collimated (laser) light source light. The laser light source light may in embodiments comprise one or more bands, having band widths as known for lasers. In specific embodiments, the band(s) may be relatively sharp line(s), such as having full width half maximum (FWHM) in the range of ≤20 nm at RT, such as ≤10 nm. Hence, the light source light has a spectral power distribution (intensity on an energy scale as function of the wavelength) which may comprise one or more (narrow) bands. The beams (of light source light) may be focused or collimated beams of (laser) light source light. The term “focused” may especially refer to converging to a small 2023PF80238 33 spot. This small spot may be at the discrete converter region, or (slightly) upstream thereof or (slightly) downstream thereof. Especially, focusing and / or collimation may be such that the cross-sectional shape (perpendicular to the optical axis) of the beam at the discrete converter region (at the side face) is essentially not larger than the cross-section shape (perpendicular to the optical axis) of the discrete converter region (where the light source light irradiates the discrete converter region). Focusing (of the laser light source light) may be executed with one or more optics, such as especially two (focusing) lenses. Collimation may be executed with one or more (other) optics, like collimation elements, such as lenses and / or parabolic mirrors. In embodiments, the beam of (laser) light source light may be relatively highly collimated, such as in embodiments ≤2° (FWHM), more especially ≤1° (FWHM), most especially ≤0.5° (FWHM). The light generating system may be part of or may be applied in e.g. office lighting systems, household application systems, shop lighting systems, home lighting systems, accent lighting systems, spot lighting systems, theater lighting systems, fiber-optics application systems, projection systems, self-lit display systems, pixelated display systems, segmented display systems, warning sign systems, medical lighting application systems, indicator sign systems, decorative lighting systems, portable systems, automotive applications, (outdoor) road lighting systems, urban lighting systems, green house lighting systems, horticulture lighting, digital projection, or LCD backlighting. The light generating system (or luminaire) may be part of or may be applied in e.g. optical communication systems or disinfection systems. In yet a further aspect, the invention also provides a lamp or a luminaire comprising the light generating system as defined herein. The luminaire may further comprise a housing, optical elements, louvres, etc. etc... The lamp or luminaire may further comprise a housing enclosing the light generating system. The lamp or luminaire may comprise a light window in the housing or a housing opening, through which the system light may escape from the housing. In yet a further aspect, the invention also provides a projection device (or “projector” or “image projector”) comprising the light generating system as defined herein. The projection device may include one or more light generating systems such as described herein. Hence, in an aspect the invention also provides a lighting device selected from the group of a lamp and a luminaire, comprising the light generating system as defined herein. In embodiment, the lighting device may further be selected from the group of a lamp, a luminaire, a projector device, a disinfection device, a photochemical reactor, and an optical 2023PF80238 34 wireless communication device. The lighting device may comprise a housing or a carrier, configured to house or support, one or more elements of the light generating system. Especially, in embodiments, the lighting device may comprise a light transmissive envelope. The light transmissive envelope may be configured at least partially enclosing the light generating system. In embodiments, the light transmissive envelope may be configured as a light window, and the system light may escape the lighting device through the light transmissive envelope. In embodiments, the light transmissive envelope may be configured to enclose the light generating system, such as especially the LED filament(s) over at least 25%, such as at least 50%, especially at least 75%, like at least 90%, including (essentially) 100%, of the circumference of the light generating system. In specific embodiments, the light transmissive envelope may be a (glass) bulb enclosing at least the LED filament(s) of the light generating system, such that the lighting device may have the appearance of a conventional light bulb. In embodiments, the light transmissive envelope may comprise a light transmissive material, such as e.g. glass and / or a light transmissive polymer. Further, in embodiments, the light transmissive envelope may comprise a light scattering material (see above), wherein the light transmissive envelope may be configured to diffuse the system light transmitted through the light transmissive envelope. In embodiments, the light transmissive envelope may thus be at least partially (diffusely) transmissive for the system light. Especially, in embodiments, the light transmissive envelope may be configured to transmit at least 70%, such as at least 80%, especially at least 90%, like at least 95%, including (essentially) 100%, of the system light. Hence, in specific embodiments, the lighting device may comprise a light transmissive envelope, wherein the light transmissive envelope may be configured at least partially enclosing the light generating system. A light transmissive envelope configured at least partially enclosing the light generating system may facilitate protecting the light generating system against ingress by dirt and / or water. Further, the light transmissive envelope may provide a decorative effect in the lighting device. BRIEF DESCRIPTION OF THE DRAWINGS Embodiments of the invention will now be described, by way of example only, with reference to the accompanying schematic drawings in which corresponding reference symbols indicate corresponding parts, and in which: Figs.1A-B schematically depict an embodiment of the light generating system; 2023PF80238 35 Figs.2A-B schematically depict further embodiments of the light generating system; Figs.3A-B schematically depict embodiments of the system light; Fig.4 schematically depicts an embodiment of the lighting device; and Fig.5 schematically depicts a further embodiment of the lighting device. The schematic drawings are not necessarily to scale. DETAILED DESCRIPTION OF THE EMBODIMENTS Fig.1A schematically depicts an embodiment of the light generating system 1000. The light generating system 1000 may especially comprise an LED filament 100 (though other embodiments may also be possible). The LED filament 100 may comprise an elongated carrier 410, a plurality of solid state light sources 10 configured on the elongated carrier 410, and an (elongated) encapsulant 420 covering the solid state light sources 10 and at least part of the elongated carrier 410. In embodiments, the solid state light sources 10 may be configured to generate blue light source light 11. Further, the encapsulant 420 may comprise a first luminescent material 210 comprising one or more luminescent materials of the type A3B5O12:Ce, wherein A comprises one or more of Y, La, Gd, Tb and Lu, and wherein B comprises one or more of Al, Ga, In and Sc. Additionally or alternatively, the encapsulant 420 may comprise a second luminescent material 220 comprising one or more luminescent materials of the type of divalent europium comprising nitride or divalent europium comprising oxynitride. Additionally or alternatively, the encapsulant 420 may comprise a third luminescent material 230 comprising one or more luminescent materials of the type M’xM2-2xAX6doped with tetravalent manganese, wherein M’ comprises an alkaline earth cation, M comprises an alkaline cation, and x is selected from the range of 0-1, wherein A comprises a tetravalent cation, for instance comprising one or more of silicon and titanium, wherein X comprises a monovalent anion, at least comprising fluorine. The luminescent materials 210,220,230 may especially be configured embedded in the encapsulant 420. Further, in embodiments, the encapsulant 420 may comprise the first luminescent material 210, second luminescent material 220, and third luminescent material 230 in a combined luminescent material concentration Cl,c. The combined luminescent material concentration Cl,cmay especially be selected from the range of 3-30 v / v%. In embodiments, the luminescent materials 210,220,230 may be configured to convert at least part of the light source light 11 into luminescent material light 211,221,231. Further, the light generating system 1000 may be configured to generate system light 1001. In embodiments, the LED 2023PF80238 36 filament 100 may be configured such that the system light 1001 comprises the luminescent material light 211,221,231 of the first luminescent material 210, the second luminescent material 220 and the third luminescent material 230, has a correlated color temperature of at maximum 2500 K and a color rendering index selected from the range of 65-78. In embodiments, the system light 1001 may further comprise at least part of the light source light 11. Especially, the system light 1001 may have a spectral power distribution in the wavelength range of 380-780 nm, wherein selected from the range of 0.1-12% of the spectral power may be in the 380-490 nm wavelength range (and may be provided by the light source light 11). The light generating system 1000 may further comprise a second encapsulant 430. The second encapsulant 430 may be configured to cover at least part of the (first) encapsulant 420. Further, the second encapsulant 430 may comprise a light scattering material 431. Additionally, the light generating system 1000 may comprise a control system 300, configured to control the spectral power distribution of the system light 1001. Further, in embodiments, the control system 300 may be configured to control the spectral power distribution of the filament light 101 generated by the LED filament 100. The filament light 101 may comprise the first, second, and third luminescent material light 211,221,231, and optionally part of the light source light 11. In embodiments, the system light 1001 may comprise the filament light 101, and may in specific embodiments consist of the filament light 101. Fig.1B schematically depicts a further embodiment of the light generating system 1000. In the embodiment of Fig.1B, the light sources 10 are configured on both major surfaces of the elongated carrier 410. Further, as depicted in Fig.1B, the light generating system 1000 may comprise (a plurality of) second light sources 20. The second light sources 20 may (also) be configured on the elongated carrier 410 (on one or both major surfaces of the elongated carrier 410). Further, the encapsulant 420 may (also) cover the second (solid state) light sources 20. In embodiments, the second light sources 20 may be configured to generate blue second light source light 21 having a second peak wavelength differing from a (first) peak wavelength of the (first) light source light 11. Hence, the control system 300 may be configured to control a spectral power distribution of the system light 1001 by controlling the (first) light sources 10 and the second light sources 20. Fig.2A schematically depicts an embodiment of the light generating system 1000, wherein the light generating system 1000 comprises a luminescent converter 200 comprising the first, second, and third luminescent materials 210,220,230. As depicted in Fig. 2023PF80238 37 2A, the (first and second) light sources 10,20 may each be configured as separate “(LED) packages” comprising a (first or second) light source 10,20 and a luminescent converter 200. In embodiments, as depicted in Fig.2A, the luminescent converter 200 may be configured on top of (and in physical contact with) the (first or second) light source 10,20. In embodiments, the control system 300 may be configured to individually control each “package” of light source 10,20 and luminescent converter 200. Fig.2B schematically depicts a further embodiment of the light generating system 1000 comprising the luminescent converter 200 and the light sources 10. As depicted in Fig.2B, the luminescent converter 200 may be configured at a non-zero distance d1from (a face of) the light sources 10. Fig.3A schematically depicts a comparison between the light generating system 1000 of the present invention and a known light generating system 2000. Data points relating to the respective light generating systems 1000,2000 are indicated using dashed boxes. The known light generating system 2000 may be configured to generate system light 2001 having a CRI of at least 80. Conversely, the light generating system 1000 of the present invention may in embodiments be configured to generate system light 1001 having a CRI of at most 80. Fig.3A schematically depicts the efficiency E (in units lumens per optical Watt, here indicated as Lm / W) of both light generating systems 1000,2000 as a function of the CIE u’ color coordinate of the second luminescent material light 221 (indicated by reference CIE- u’red). As depicted in Fig.3A, the light generating system 1000 displays a higher efficiency E at a similar CIE-u’redvalue as the known light generating system 2000. Hence, the light generating system 1000 of the present invention may especially have as a benefit that the efficiency of the light generating system 1000 may be improved compared to known systems. Fig.3B schematically depicts embodiments of the system light 1001 provided using the data points showing the highest efficiency E in Fig.3A. Especially, Fig.3B schematically depicts the highest value for the CIE u’ color coordinate of the second luminescent material light 221 that may be used at different CCTs of the system light 1001, in order to provide system light 1001 with a high efficiency 1001. Especially, Fig.3B depicts the CIE-u’redfor which applies that: CIE-u’red= c1*[0.5+(0.9538-0.000837*TC)*Pabr]. In embodiments, if the CIE-u’redof a light generating system 1000, especially of a LED filament 100, is located on or below (yet close to) the lines depicted in Fig.3B, said light generating system 1000 may be relatively more efficient. That is, a light generating system 1000 providing system light 1001 with a color point of the second luminescent material light 221 and a Pabrlocated above the line for the respective CCT in Fig.3B may be less efficient (yet 2023PF80238 38 may have a higher CRI) than a light generating system 1000 providing said system light 1001 with a color point of the second luminescent material light 221 and a Pabrlocated below the line for the respective CCT in Fig.3B. Hence, the LED filament 100 (of the present invention) may be configured such that the following applies: CIE-u’red≤ c1*[0.5+(0.9538- 0.000837*TC)*Pabr], wherein CIE-u’redis the CIE u’ color coordinate of the second luminescent material light 221, c1 is selected from the range of 0.9-1.1, TCis the (selected) correlated color temperature of the system light 1001, and Pabris the factor of the spectral power of the light source light 11 that is converted by the third luminescent material 230. In embodiments, TCmay be selected from the range of 1600-2500 K, especially from the range of 1600-2200 K. Further, Pabrmay be selected from the range of 0.03-0.4. In specific embodiments, Pabr≥ 0.1. Further, in embodiments, CIE-u’redmay be at least 0.3. The (maximum) value for CIE-u’redmay thus depend on the factor of the spectral power of the light source light 11 that is converted by the third luminescent material 230. Hence, the (blue) light source light 11 may have a spectral power distribution, such as especially in the wavelength range of 380-780 nm, wherein a part of the spectral power may be converted by the third luminescent material 230. Especially, the blue light source light 11 may have a spectral power distribution, and the LED filament 100 may be configured such that between 3-10% of the spectral power of the blue light source light 11 may be converted by the third luminescent material 230. Fig.4 schematically depicts an embodiment of a luminaire 2 comprising the light generating system 1000 as described above. Reference 301 indicates a user interface which may be functionally coupled with the control system 300 comprised by or functionally coupled to the light generating system 1000. Fig.4 also schematically depicts an embodiment of lamp 1 comprising the light generating system 1000. Reference 3 indicates a projector device or projector system, which may be used to project images, such as at a wall, which may also comprise the light generating system 1000. Hence, Fig.4 schematically depicts embodiments of a lighting device 1200 selected from the group of a lamp 1 and a luminaire 2, comprising the light generating system 1000 as described herein. In embodiments, such lighting device may be a lamp 1, a luminaire 2, a projector device 3, a disinfection device, or an optical wireless communication device. Lighting device light escaping from the lighting device 1200 is indicated with reference 1201. Lighting device light 1201 may essentially consist of system light 1001, and may in specific embodiments thus be system light 1001. Reference 1300 refers to a space, such as a room. 2023PF80238 39 Fig.5 schematically depicts a further embodiment of the lighting device 1200 comprising the light generating system 1000. The lighting device 1200 may comprise a light transmissive envelope 610. The light transmissive envelope 610 may especially be configured at least partially enclosing the light generating arrangement 1000. Further, as depicted in Fig.5, the light generating system 1000 may (further) comprise a second LED filament 120. The (first) LED filament 100 may especially be configured to generate (first) filament light 101, and the second LED filament 120 may be configured to generate second filament light 121. In embodiments, the (first) LED filament 100 and the second LED filament 120 may differ in relative amounts of the luminescent materials 210,220,230. Hence, the (first) filament light 101 and the second filament light 121 may differ in one or more of spectral power distribution and CCT. Especially, system light 1001 based on the (first) LED filament 100 only may have a first correlated color temperature TC1and system light 1001 based on the second LED filament 120 only may have a second correlated color temperature TC2, wherein | TC1- TC2| ≥ 1000 K. In embodiments, the control system 300 may (thus) be configured to control a spectral power distribution of the system light 1001 by controlling the (first) light sources 10 comprised by the (first) LED filament 100 and the (first) light sources 10 comprised the second LED filament 120. The term “plurality” refers to two or more. The terms “substantially” or “essentially” herein, and similar terms, will be understood by the person skilled in the art. The terms “substantially” or “essentially” may also include embodiments with “entirely”, “completely”, “all”, etc. Hence, in embodiments the adjective substantially or essentially may also be removed. Where applicable, the term “substantially” or the term “essentially” may also relate to 90% or higher, such as 95% or higher, especially 99% or higher, even more especially 99.5% or higher, including 100%. The term “comprise” also includes embodiments wherein the term “comprises” means “consists of”. The term “and / or” especially relates to one or more of the items mentioned before and after “and / or”. For instance, a phrase “item 1 and / or item 2” and similar phrases may relate to one or more of item 1 and item 2. The term "comprising" may in an embodiment refer to "consisting of" but may in another embodiment also refer to "containing at least the defined species and optionally one or more other species". Use of the verb "to comprise" and its conjugations does not exclude the presence of elements or steps other than those stated in a claim. Unless the context clearly requires otherwise, throughout the description and the claims, the words “comprise”, “comprising”, and the like are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense; that is to say, in the sense of “including, but not limited 2023PF80238 40 to”. The article "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. Furthermore, the terms first, second, third and the like in the description and in the claims, are used for distinguishing between similar elements and not necessarily for describing a sequential or chronological order. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the invention described herein are capable of operation in other sequences than described or illustrated herein. The devices, apparatus, or systems may herein amongst others be described during operation. As will be clear to the person skilled in the art, the invention is not limited to methods of operation, or devices, apparatus, or systems in operation. It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. The invention may be implemented by means of hardware comprising several distinct elements, and by means of a suitably programmed computer. In a device claim, or an apparatus claim, or a system claim, enumerating several means, several of these means may be embodied by one and the same item of hardware. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. In yet a further aspect, the invention (thus) provides a software product, which, when running on a computer is capable of bringing about (one or more embodiments of) the method as described herein. The invention also provides a control system that may control the device, apparatus, or system, or that may execute the herein described method or process. Yet further, the invention also provides a computer program product, when running on a computer which is functionally coupled to or comprised by the device, apparatus, or system, controls one or more controllable elements of such device, apparatus, or system. The invention further applies to a device, apparatus, or system comprising one or more of the characterizing features described in the description and / or shown in the attached drawings. The invention further pertains to a method or process comprising one or more of the characterizing features described in the description and / or shown in the attached drawings. The various aspects discussed in this patent can be combined in order to provide additional advantages. Further, the person skilled in the art will understand that embodiments 2023PF80238 41 can be combined, and that also more than two embodiments can be combined. Furthermore, some of the features can form the basis for one or more divisional applications.

Claims

2023PF80238 42 CLAIMS:

1. A light generating system (1000) comprising an LED filament (100), wherein the LED filament (100) comprises an elongated carrier (410), a plurality of solid state light sources (10) configured on the elongated carrier (410), and an encapsulant (420) covering the solid state light sources (10) and at least part of the elongated carrier (410), wherein: - the solid state light sources (10) are configured to generate blue light source light (11); - the encapsulant (420) comprises (i) a first luminescent material (210) comprising one or more luminescent materials of the type A3B5O12:Ce, wherein A comprises one or more of Y, La, Gd, Tb and Lu, and wherein B comprises one or more of Al, Ga, In and Sc, (ii) a second luminescent material (220) comprising one or more luminescent materials of the type of divalent europium comprising nitride or divalent europium comprising oxynitride, and (iii) a third luminescent material (230) comprising one or more luminescent materials of the type M’xM2-2xAX6doped with tetravalent manganese, wherein M’ comprises an alkaline earth cation, M comprises an alkaline cation, and x is selected from the range of 0-1, wherein A comprises a tetravalent cation, for instance comprising one or more of silicon and titanium, wherein X comprises a monovalent anion, at least comprising fluorine; wherein the luminescent materials (210,220,230) are configured to convert at least part of the light source light (11) into luminescent material light (211,221,231); and - the light generating system (1000) is configured to generate system light (1001), wherein the LED filament (100) is configured such that the system light (1001) comprises the luminescent material light (211,221,231) of the first luminescent material (210), the second luminescent material (220), and the third luminescent material (230), has a correlated color temperature of at maximum 2500 K and a color rendering index selected from the range of 65-78; and - wherein the LED filament (100) is configured such that the following applies: CIE-u’red≤ c1*[0.5+(0.9538-0.000837*TC)*Pabr], wherein CIE-u’redis the CIE u’ color coordinate of the second luminescent material light (221), c1 is selected from the range of 0.9-1.1, TCis the correlated color temperature of the system light (1001), and Pabris the factor2023PF80238 43 of the spectral power of the light source light (11) that is converted by the third luminescent material (230), and wherein Pabris selected from the range of 0.03-0.

4.

2. The light generating system (1000) according to claim 1, wherein the first luminescent material (210) comprises a luminescent material of the type A3B5O12:Ce, wherein A at least comprises Lu.

3. The light generating system (1000) according to claim 1, wherein the first luminescent material (210) comprises a luminescent material of the type A3B5O12:Ce, wherein A at least comprises Y, and wherein B at least comprises Ga.

4. The light generating system (1000) according to any one of the preceding claims, wherein the second luminescent material (220) comprises one or more of (Ba,Sr,Ca)AlSiN3:Eu, (Ba,Sr,Ca)2Si5N8:Eu, and SrLi2Si2Al2O2N2:Eu.

5. The light generating system (1000) according to any one of the preceding claims, wherein the third luminescent material (220) comprises one or more of (K,Rb)2SiF6:Mn4+, (K,Rb)2TiF6:Mn4+, K2(Si,Ti)F6:Mn4+, and Rb2(Si,Ti)F6:Mn4+.

6. The light generating system (1000) according to any one of the preceding claims, wherein the system light (1001) has a spectral power distribution in the wavelength range of 380-780 nm, wherein selected from the range of 0.1-12% of the spectral power is in the 380-490 nm wavelength range.

7. The light generating system (1000) according to any one of the preceding claims, wherein the blue light source light (11) has a spectral power distribution, wherein the LED filament (100) is configured such that between 3-10% of the spectral power of the blue light source light (11) is converted by the third luminescent material (230).

8. The light generating system (1000) according to any one of the preceding claims, wherein TCis selected from the range of 1600-2200 K.

9. The light generating system (1000) according to claim 8, wherein CIE-u’redis at least 0.3.2023PF80238 44 10. The light generating system (1000) according to any one of the preceding claims 8-9, wherein Pabr≥ 0.

1.

11. The light generating system (1000) according to any one of the preceding claims, wherein the encapsulant (420) comprises the first luminescent material (210), second luminescent material (220), and third luminescent material (230) in a combined luminescent material concentration Cl,c, wherein the combined luminescent material concentration Cl,cis selected from the range of 3-30 v / v%.

12. The light generating system (1000) according to any one of the preceding claims, wherein the LED filament (1000) further comprises a second encapsulant (430), wherein the second encapsulant (430) is configured to cover at least part of the encapsulant (420), and wherein the second encapsulant comprises a light scattering material (431).

13. The light generating system (1000) according to any one of the preceding claims, further comprising a control system (300) and second light sources (20); wherein the second light sources (20) are configured on the elongated carrier (410); wherein the encapsulant (420) covers the second light sources (20); wherein the second light sources (20) are configured to generate blue second light source light (21) having a second peak wavelength differing from a peak wavelength of the light source light (11); and wherein the control system (300) is configured to control a spectral power distribution of the system light (1001) by controlling the solid state light sources (10) and the second light sources (20).

14. The light generating system (1000) according to any one of the preceding claims, further comprising second LED filament (120); wherein the LED filament (100) and the second LED filament (120) differ in relative amounts of the luminescent materials (210,220,230); wherein the system light (1001) based on the LED filament (100) only has a first correlated color temperature TC1and wherein the system light (1001) based on the second LED filament (120) only has a second correlated color temperature TC2, wherein |TC1- TC2| ≥ 1000 K; and wherein the control system (300), as defined in claim 13, is configured to control a spectral power distribution of the system light (1001) by controlling the solid state light sources (10) comprised by the LED filament (100) and the solid state light sources (10) comprised the second LED filament (120).2023PF80238 45 15. A lighting device (1200) selected from the group of a lamp (1) and a luminaire (2), comprising the light generating system (1000) according to any one of the preceding claims; wherein the lighting device (1200) comprises a light transmissive envelope (610), wherein the light transmissive envelope (610) is configured at least partially enclosing the light generating system (1000).

Images